Pivot drive for manipulator

Abstract

A pivot drive for interconnecting a pair of members that are relatively pivotal about a pivot axis has a torsion rod extending along a rod axis and rotatable by an appropriate drive relative to one of the members. This rod has outer ends carrying input gears of respective constant-mesh gear trains having output gears at least one of which is limitedly rotatable about the pivot axis on the other member. This one output gear can be limitedly rotated and locked in place in the other member so as torsionally to prestress the rod, thereby eliminating play from the drive by bringing the gears of one of the gear trains into snug contact in one direction and the gears of the other gear train into snug contact in the opposite directions.

I claim: 
     
       1. A pivot drive for interconnecting a pair of members that are relatively pivotal about a pivot axis, said drive comprising: a torsion rod extending along a rod axis and having outer ends;   drive means for rotating said rod about said rod axis relative to one of said members;   respective constant-mesh gear trains including respective input gears fixed on said outer ends and respective output gears connected to the other of said members and having respective centers, at least one of said output gears being limitedly angularly displaceable about the respective center relative to said other member; and   means for rotating said one output gear relative to said other member about the respective center and thereby torsionally prestressing said rod and for locking said one output gear in position with said torsion rod prestressed.   
     
     
       2. The drive defined in claim 1 wherein said centers form an output-gear axis and all of said axes are coaxial. 
     
     
       3. The drive defined in claim 2 wherein said other member is carried on said output gears. 
     
     
       4. The drive defined in claim 3 wherein said one output gear is formed relative to the respective center with a tangentially extending surface, said means for rotating including: a bar lying on said surface and having bar ends; and   respective bolts threaded in said other member and bearing in a direction generally toward the respective center on said bar ends, whereby said bolts can be screwed in said other member to displace said bar ends relative to said other member and to rotate said one output gear in said other member about the respective center.   
     
     
       5. The drive defined in claim 2 wherein said other member is forked and has a pair of axially spaced sides respectively holding said gear trains. 
     
     
       6. The drive defined in claim 2 wherein said drive means is connected to said torsion rod between said outer ends thereof. 
     
     
       7. The drive defined in claim 6 wherein said torsion rod has a pair of halves respectively having said outer ends and joined together between said outer ends at a geometric center, said drive means being connected to said rod at said geometric center. 
     
     
       8. The drive defined in claim 7 wherein at least one of said halves is a tube shaft, said drive means including a drive shaft extending coaxially through said tube shaft to said geometric center. 
     
     
       9. The drive defined in claim 8 wherein said halves are splined onto said drive shaft at said geometric center. 
     
     
       10. The drive defined in claim 9 wherein said halves are substantially identical tube shafts. 
     
     
       11. The drive defined in claim 9 wherein said drive means includes a bearing between said outer end of said tube shaft and said drive shaft. 
     
     
       12. The drive defined in claim 1 wherein said centers define an output-gear axis, said pivot axis coinciding with one of said rod and output-gear axes. 
     
     
       13. The drive defined in claim 1 wherein said gear trains are planetary-gear assemblies. 
     
     
       14. The drive defined in claim 13 wherein said assemblies each have: a sun gear constituting the respective input gear,   a planet carrier constituting the respective output gear,   a plurality of planet gears carried by said carrier and meshing with said sun gear, and   a ring gear meshing with said planet gears and fixed on said one member.